Device for discharging molten metal from a container

ABSTRACT

A device for discharging molten metal from a container to another, comprising an outlet sleeve which penetrates into the lower container pushed by springs against a nozzle of refractory material which connects the inside of the upper container with the outside, so as to make a seal for the molten metal. The outlet sleeve is surrounded by a cylindrical sheath which joins, through a sand joint with a cylindrical blade fixed to the base of the upper container, around the aperture where it faces the nozzle. The sheath and the blade enclose a volume into which an inert gas is injected to remove the air possibly present.

FIELD OF THE INVENTION

The invention refers to a device for discharging molten metal from onecontainer to another, from example from a ladle to a tundish or from atundish to an under tundish for feeding a continuous casting line.

STATE OF THE ART

Normally, in continuous casting plants, the molten metal whichoriginates, for example from an electric furnace, or from a converter,is subjected to a series of pouring passages between containers, priorto being cast in the ingot mould to form ingots, slabs, bars, strips andothers.

A typical example is given by the application of the technology ofcontinuous strip casting in which the steel emerging from the productionoven is collected in a ladle, from which it is unloaded into one or moretundishes, each of which feeds one or more melts above two cooled,counter rotating casting rolls, which form the ingot mould in which themetal solidifies and emerges in the form of finished product, forexample a strip, a bar or otherwise. Amongst the tundish and the ingotmould can also be envisaged an under tundish, from which the moltenmetal passes into the ingot mould.

It is known that the quality of the final product, and also theexecution of the process itself can be compromised by the contact of airwith the molten metal. For example, the oxygen of the air can combinewith elements dissolved in the steel forming inclusions, whichdeteriorate the quality of the steel, as also with dissolved oxygenitself. In the case in which the steel is used in continuous casting,for example in a dual roller plant, the oxygen combined with the ironcan produce scale which deposits on the rolls, locally altering, amongstothers, the heat exchange, with serious consequences for the finalproduct. Nitrogen can also cause the formation of precipitates whichcompromise the quality of the product.

In the containers into which the molten metal must pass there isgenerally maintained a protective atmosphere, generally through thefeeding of an inert gas, for example argon.

The various passages of the metal from one container to another arecritical, with regard to the problem of possible contamination with air,bearing also in mind that the various containers must be emptied inbetween, both for the normal movement during the metal productionoperation, as for example in the case of the tundishes, and to allow forthe substitution of the parts in refractory material, such as forexample the outlet sleeves through which the molten metal flows, whichare subject to rapid wear and corrosion.

Discharging devices in the known art are not easy to operate and requiredelicate operations to allow the approaching of two containers forjoining. Sometimes collisions produced during the coupling damage partsof the discharging device.

Therefore, the need is felt to provide a discharging device, tointerpose between the various containers in which the molten metalpasses, which allows avoiding contact between the air and the metal andwhich allows a rapid and precise coupling between the containers, inaddition to a likewise rapid uncoupling.

SUMMARY OF THE INVENTION

It is therefore an aim of the present invention, to overcome the abovementioned problems by providing a device for discharging molten metalfrom a container which allows a rapid and precise coupling of thecontainer to another container so as to constitute a conduit for thepassage of the molten metal which avoids the contact of the metal withthe air.

A further aim is that of providing a discharging device which allows arapid, reliable and lasting coupling of the two containers, in thepresence of molten metal at high temperature and which in addition isnot is not prone to the impacts which occur during coupling of thecontainers.

The problems exposed above have been solved according to the main claimby means of a discharging device for molten metal between a first uppervessel and a second container placed below the first one in which saidfirst container comprises a circular blade, fixed to the base of thefirst container around an aperture, a nozzle, inserted in said aperturewith the lower extremity protruding from it and in which said secondcontainer comprises an outlet sleeve the upper extremity of which issuitable to be coupled with said lower extremity of the nozzle, elasticmeans for pushing said outlet sleeve upwards, a cylindrical sheathsurrounding said nozzle and said elastic means, means of sealing gasbetween said sheath and said circular blade.

Generally, said outlet sleeve is placed with its vertical axis andpenetrates into the lower container with its lower extremity, through anappropriately made hole in the cover of the latter. The sheath can beadvantageously cylindrical, as with the blade, and be coaxial with theoutlet sleeve, and be welded to the lower container, around saidopening. Preferably said means for realising a gas seal are sand joints.The blade is preferably welded to the base of the upper container.

Coupling the lower extremity of the nozzle with that uppermost of theoutlet sleeve one creates a channel which connects the interiors of thetwo containers. A force supplied by appropriate means guarantees sealingwith respect to the molten metal.

LIST OF THE FIGURES

Further advantages of the present invention will become evident, to theskilled person, from the following detailed description of a particularembodiment given by way of non limiting example, of a discharging devicewith reference to the following figures, of which:

FIG. 1 shows a section of a casting plant in which is used a dischargingdevice according to the present invention which connects a tundish withan under tundish;

FIG. 2 shows an enlarged section of the discharging device according tothe invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to the cited figures is described, a preferred embodimentof a discharging device according to the present invention whichconnects the base 1 of a tundish to an under tundish 2 or also of aladle with a tundish.

The cylindrical metal sheath 3, is welded to a plate 4 integral with theunder tundish 2. The outlet sleeve 5 through the hole crosses the plate4 and the upper walls 7 of the under tundish 2. The outlet sleeve 5 hasa ring shaped protrusion 8 around its upper extremity. On the protrusion8 act the means for pushing the outlet sleeve upwards and holding itvertically, comprising a helical spring 9, or equivalent elastic means,a metallic beaker 10, having internally a metallic ring shaped support11 which holds a ring 12 of refractory material into which the nozzle 5is inserted. The spring 9 reacting against the plate 4 acts on thebeaker 10, pushing the latter upwards and thus also the nozzle 5. Astructure for centring the spring 9 and the beaker 10 can be envisaged.In the case in the figure it is represented by a metal cylinder 13,surrounded by the spring 9, and around which runs the beaker 10. A tube14 of refractory material is fixed to it with a spacer of refractorymaterial adequate 24, for the protection of the spring 9 and thecylinder 13 from heat. The outlet sleeve 5 can run in the tube 14,pushed by the spring 9. Preferably spring 9 and cylinder 13 are coaxialto the outlet sleeve 5. The beaker 10 can run on the cylinder 13.

The blade 15, Fixed to the plate 16, making part of the base 1 of thetundish, is cylindrical and is of shape and size such that its loweredge can penetrate into the ring shaped tank 17, filled with sand 26 orother appropriate material, said tank surrounding the upper edge of thesheath 3, thus realising a sand joint for the sealing of gas.

The structure 18, making part of the base 1 of the tundish, holds anozzle 19 of refractory-material, the lower end of which faces theopening 20. The duct of the nozzle 19 connects the inside of the tundish1 with the outside.

When the coupling placing the tundish 1 over the under tundish 2, isrealised as indicated in FIG. 1, and at the same time forming a gas sealby sinking the ring shaped blade 15 into the sand 26, the spring 9pushes the outlet sleeve 5 against the nozzle 19, thus forming a channelwhich connects the insides of the two containers, and a secure seal forthe molten metal destined to flow through the channel.

It could be advantageous that the duct of the nozzle 19 is of aninferior diameter than the duct of the outlet sleeve 5.

The surfaces of the nozzle 19 and of the outlet sleeve 5 adapted to becoupled can have different appropriate shapes. According to a preferredaspect, they can be spherical surfaces, one concave and one convex,which allows the auto-alignment of the ducts of the nozzle 19 and theoutlet sleeve 5 when coupling is made.

A tube 21 crosses the blade 15, said tube 21 being destined to feed-ingasses of appropriate composition, for example argon, inside thering-shaped chamber 25 formed in the space enclosed by the blade 15 andthe sheath 3 thanks to the sand joint. The gas has the aim to avoid theentry of air and to dilute and remove any residual air possiblyentrapped. A gas distribution system, for example comprising aring-shaped distribution chamber 22, formed between the blade 15 and theplate 16, can be envisaged in which the tube 21 introduces the gas andpossesses a series of holes 23 to distribute it uniformly all along thecircumference of the device. Alternatively, more feeling tubes along theperimeter of the blade can be envisaged 15. If deemed appropriate, gasfeeding tubes which cross the sheath 3 or other parts of the device canbe envisaged.

The characteristics of the spring 9 are advantageously selected so as tohave force to push the outlet sleeve 5 against the nozzle 19 adequate tothe requirements. The weight of the outlet sleeve 5 holds it in positionalso when the coupling between the containers is not realised.

With a device such as that represented, the passage of molten metal canbe regulated or blocked by a standard system buffer shaft 30 present inthe upper container. With appropriate skill the device of the inventioncan be adapted for different discharging systems, such as that of thethree plate box. It should be clarified that the base of the uppercontainer can also comprise other elements, in addition to thesedescribed above, such as, in fact a box discharging system, of the typein which a mobile hold plate of refractory material is interposedbetween two fixed hold elements, for example two nozzles. The movementof the plate aligns or hides the hole to the ducts of the nozzles,closing or opening the passage to the molten metal. In such a case, thering shaped blade can be fixed to the base of the box discharging systemand the lower nozzle of it is adapted to be coupled with the outletsleeve of the lower part of the device according to the invention.

1. A molten metal discharging device between a first upper container (1)and a second container placed below the first container wherein saidfirst container comprises a ring shaped blade (15), fixed to the base ofthe first container around a molten metal discharging aperture (20), anozzle (19), inserted into said aperture with the lower end protrudingfrom it and in which said second container (2) comprises an outletsleeve (5) the lower end of which is suitable for being coupled withsaid lower end of the nozzle (19), elastic means (9, 10, 11, 12) adaptedto push said outlet sleeve upwards, a cylindrical sheath (3) surroundingsaid outlet sleeve (5) and said elastic means, gas sealing means (17)between said sheath (3) and said ring shaped blade (15).
 2. The deviceaccording to claim 1 wherein in the operating position of couplingbetween said first and second containers, said sheath (3) and said ringshaped blade (15) delimit a ring shaped gas tight chamber (25).
 3. Thedevice according to claim 2 wherein there are provided gas supplyingmeans (21) for supplying gas to the interior of said ring shapedchamber.
 4. The device according to claim 1 wherein said nozzle (19) andsaid outlet sleeve (5) are of refractory material.
 5. The deviceaccording to claim 1 wherein said blade (15) and said sheath (3) arecoaxial with said outlet sleeve (5).
 6. The device according to claim 1wherein said elastic means (9, 10, 11, 12) comprise a helical springwhich imposes a force in the axial direction on the outlet sleeve (5).7. The device according to claim 6 wherein said spring (9) is coaxialwith the outlet sleeve (5) and a beaker (10) is interposed between thespring itself and the outlet sleeve (5), wherein a force is transmittedby the spring to the outlet sleeve (5) through said beaker.
 8. Thedevice according to claim 1 wherein said outlet sleeve (5) penetratesinside the lower container.
 9. The device according to claim 1 whereinsaid gas sealing means (17) between said sheath and said blade comprisea sand joint.
 10. The device according to claim 1 wherein a duct of saidnozzle (19) has a diameter inferior to that of a duct of said outletsleeve (5).
 11. The device according to claim 3 wherein said gassupplying means (21) comprise a tube which crosses said blade (15) and aring shaped distribution chamber (22).